Welcome to the forum. Sorry about desi. I dont think your frog died of starvation just from not being fed a couple of days.... If I may say, frogs can last up to a month(ussually) without food in the wild. Soooo. I would highly doubt they died from starvation. Did you look into the care they were giving them? Ussually petstores even specialty ones tend to give bad care to their animals. You may need to take that animal to the vet and check its health. Just to be safe. Other than that, if you do want a another frog you could buy them on certain good online sites or just go to a reptile expo. Ussually both have good ones. I say this because I sympathize with you. Ive had similar experience with petstores. But anywho. If the dumpy is below 3inches feed pinheads. If its 3inches feed mediums, if its a "large" dumpy well now you can feed them these:
Crickets<--dusted weekly
Waxworms<---they love these
Butterworms<--If you find them they're also good
Earthworms<---good to get the frog a tad fatter(alot of meat)
Locusts<---very rare but nutritious
Grasshoppers-same as the locust
Moths<---frogs and toads absolutely love these!

For the most part I would feed insects that are "captive" rather than catching them. For moths what you can do is you can either just cultivate your own batch by grabbing a few moth eggs(try as many). Then try getting them to reproduce. I dont know how hard it would be. But yeah. I remember seeing some places that sell them. But I forget their names. Anywho good luck with your white's treefrog(s). These lil buggers are cute as a button and easy to care for.